1. Field
The present disclosure relates to microfluidic apparatuses for isolating target cells in a biological sample and methods of enriching target cells by using the microfluidic apparatuses.
2. Description of the Related Art
Death of a patient caused by a malignant tumor is mostly due to metastasis of the tumor from a site where the tumor originally occurred to other tissues or organs. Accordingly, in order to increase the chance of survival for a cancer patient, it is very important to discover tumor metastasis early; early discovery of the tumor and monitoring the growth of the tumor are regarded as major elements for successful treatment of the patient. In general, cancer is diagnosed by histopathology. Histopathology is a diagnosis method wherein a tissue sample obtained from a biopsy specimen is used to directly identify tumor cells. However, a tissue selected to obtain a biopsy specimen sample may not contain a tumor, and since only data about a particular site obtained from the biopsy specimen is provided, identifying metastasis of a tumor to other sites is quite limited. Accordingly, use of histopathology in diagnosing or monitoring tumors has many limitations.
Circulating tumor cells (CTCs) can be identified in patients before a tumor is originally detected, and CTCs may play an important factor in diagnosing cancer early. In addition, since cancer spreads through blood in most cases, CTCs may be used as a marker for identifying cancer metastasis. In addition, CTCs can be detected even after cancer cells are removed by a surgical operation, and in this case, the possibility of recurrence of cancer is very high. However, since the amount of CTCs in blood may be very small (for example few CTC cells per mL of blood) and the CTCs are very fragile, it is difficult to correctly identify the number of CTCs. Accordingly, there is a need to develop a diagnosis method with high sensitivity in detecting CTCs, cancer cells, or cancer stem cells present in the body of patients. In order to obtain a sufficient amount of CTC cells for an accurate detection, an apparatus which can process a relatively large amount of blood (for example up to about 20 mL) is needed as well.
Red blood cells, white blood cells/circulating tumor cells, or a serum may be manually separated from a density gradient in order to isolate CTCs, cancer cells, or cancer stem cells. However, layer of white blood cells/circulating tumor cells is very thin, and thus, manually separating the layer of white blood cells/circulating tumor cells based on the density gradient is difficult and also separation reproducibility largely depends on the ability of the person who performs the separation.